Re: [PATCH 2/3] x86: Add support for AMD's Automatic IBRS

[Jason Andryuk <jandryuk@xxxxxxxxx>]

On Fri, May 26, 2023 at 11:01 AM Alejandro Vallejo
<alejandro.vallejo@xxxxxxxxx> wrote:
>
> In cases where AutoIBRS is supported by the host:
>
> * Prefer AutoIBRS to retpolines as BTI mitigation in heuristics
>   calculations.
> * Always enable AutoIBRS if IBRS is chosen as a BTI mitigation.
> * Avoid stuffing the RAS/RSB on VMEXIT if AutoIBRS is enabled.
> * Delay setting AutoIBRS until after dom0 is set up, just like setting
>   SPEC_CTRL.
>
> Signed-off-by: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
> ---

> --- a/xen/arch/x86/spec_ctrl.c
> +++ b/xen/arch/x86/spec_ctrl.c
> @@ -390,7 +390,7 @@ custom_param("pv-l1tf", parse_pv_l1tf);

> @@ -399,7 +399,10 @@ static void __init print_details(enum ind_thunk thunk)
>      if ( max >= 2 )
>          cpuid_count(7, 2, &tmp, &tmp, &tmp, &_7d2);
>      if ( boot_cpu_data.extended_cpuid_level >= 0x80000008 )
> +    {
>          cpuid(0x80000008, &tmp, &e8b, &tmp, &tmp);
> +        cpuid(0x80000021, &e21a, &tmp, &tmp, &tmp);
> +    }

Do you need to check boot_cpu_data.extended_cpuid_level >= 0x80000021?

Regards,
Jason